Modeling for 3D Printing: You will want to keep in mind that no matter how large things look on your screen, they will eventually be scaled down to fit on your printer's build-plate.
SketchUp allows for 2D exports as either raster or vector formats. The more detail you add in, the larger your eventual file will be, which could eventually lead to some performance issues. Modeling for 2D Rendering: You can put as much detail as you want into a model that will only exist within Sketchup. The level of detail you include in a 3D model should be a balance between what the eventual model needs to do, and how good you want it to look on screen.
